A USA TODAY article explains that early exposure to pets, peanuts and intestinal worms might actually be good for you because they program the developing immune system to know the difference between real threats, such as germs, and non-threats, like pets.

Evidence has been mounting for more than a decade. But now researchers are beginning to test remedies based on these theories in patients. Other doctors are trying to make use of novel approaches to retrain the immune system once it's too late and allergies set in.

To test whether high-dose exposure breeds tolerance, researchers are preparing to launch a counterintuitive, seven-year, U.S.-financed study that will expose infants to peanuts. It's based on research showing that children who eat peanuts at an early age are less likely to develop peanut allergies.

A second team of researchers, led by Patrick Holt of the University of Western Australia in Perth, will conduct a similar study in which children who are already allergic to other substances will be exposed to airborne allergens such as ragweed to see whether it will block the development of other allergies.